Antioxidant activity of Maillard type reaction products between phosphatidylethanolamine and glucose

Maillard reaction products derived from xylose-phosphatidylethanolamine: Potential anti-oxidative substances from hot-pressed flaxseed oil

Hot-pressed flaxseed oil is favored in Northwest China as cooking oil due to its flavor and oxidative stability. The mechanism of enhancing oxidation stability of hot-pressed flaxseed oil by neoformed Maillard reaction products (MRPs) remains mysterious. Maillard model reaction between phosphatidylethanolamine (PE) and reducing sugar of flaxseed, glucose (Glu)/fructose (Fru)/xylose (Xyl), was conducted to investigate the antioxidant characteristics of products. MRPs of PE-Xyl had a superior reactivity and anti-oxidative capabilities, which could improve the oxidative stability of flaxseed oil and inhibited the formation of aldehydes in the accelerated oxidation. Phosphatidylethanolamine-linked pyrrolecarbaldehyde (PLP) was the main antioxidant component in MRPs of Xyl-PE by MS and NMR analysis and verification of antioxidant activity. Furthermore, the results of quantum chemical calculation show that the antioxidant activity center of PLP is the pyrrole group. The findings of this study provide insights into the chemical basis underlying the improved oxidative stability of hot-pressed oils.

Effect of soybean phosphatidylethanolamine-tamarind gum Maillard conjugate on physicochemical stability of water-in-oil emulsions

Lipid oxidation hinders the development of water-in-oil (W/O) emulsions. This work aimed to determine the impact of soybean phosphatidylethanolamine (SP)/tamarind gum (TG) ratios on interface activity and anti-oxidant capacity of Maillard conjugates (MCs) in W/O emulsions. Results showed that grafting degree of MCs reached maximum with SP/TG ratio at 1:1 (43.5 %). Compared with SP and mixtures, interface activity (larger reduction of interfacial tension) and anti-oxidant capacity of MCs, especially with SP/TG = 1:1, were enhanced. The improvement of interface activity was owing to more stable adsorption at the interface caused by the increase of zeta potential and water contact angle as well as faster interface saturation benefited from broader steric network of TG moiety. The higher DPPH scavenging ability and ferric-reducing antioxidant power of MC were attributed to the combined effects of grafting degree, interface activity and molecule behavior of TG moiety. When the MC was added, the emulsion was observed smaller droplet size (1.3 μm), higher zeta potential (-73.5 mV) and lower contents of primary and secondary oxidation products (decreased by 70.9 % and 78.7 %, respectively). Hence, soybean phosphatidylethanolamine-tamarind gum-Maillard conjugate was effective to improve the physicochemical stability of W/O emulsions.

Unraveling the Formation Mechanism of Egg's Unique Flavor via Flavoromics and Lipidomics

Egg products after thermal treatment possess a unique flavor and are favored by consumers. In this study, the key aroma-active compounds of egg yolk products and their formation mechanism during thermal treatment were investigated. The volatile aroma compounds in egg yolks were monitored using an electronic nose, gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry-mass spectrometry (GC-O-MS), and the lipid molecular species were explored using ultra-high-performance liquid chromatography- mass spectrometry with a Q-Exactive HF-X Orbitrap (UPLC-Q-Exactive HF-X). A total of 68 volatile compounds were identified. Boiled eggs mainly derived their flavor from hexanal, 2-pentyl-furan, 2-butanone, 3-methyl-butanal and heptane. Meanwhile, fried eggs relied mainly on 14 compounds, the most important of which were 2-ethyl-3-methyl-pyrazine, 3-ethyl-2,5-dimethyl-pyrazine, 2-ethyl-3,5-dimethyl-pyrazine, nonanal and 2,3-diethyl-5-methyl-pyrazine, providing a baked and burnt sugar flavor. A total of 201 lipid molecules, belonging to 21 lipid subclasses, were identified in egg yolks, and 13 oxidized lipids were characterized using a molecular network. Phosphoethanolamines (PEs) containing polyunsaturated fatty acids were the primary flavor precursors contributing to the development of egg yolks' flavor, participating in lipid oxidation reactions and the Maillard reaction and regulating the production of aldehydes and pyrazine compounds. This study provides reference and guidance for the development of egg yolk flavor products.

Effect of Vacuum Roasting on Total Selenium Content of Selenium-Enriched Rapeseed, Maillard Reaction Products, Oxidative Stability and Physicochemical Properties of Selenium-Enriched Rapeseed Oil

Selenium-enriched rapeseed (SER) is an emerging oil seed. Roasting is beneficial in improving oil yield and promoting the release of micronutrients into SER oil, but high temperatures and dry air lead to selenium loss and fatty acid degradation in SER. To minimize the selenium loss and improve the SER oil quality, this study investigated the effects of vacuum (VC) roasting (90-170 °C for 30 min) on the SER selenium content, Maillard reaction products, oxidative stability, and physicochemical properties of SER oil, with conventional dry air (DA) roasting as the control. The results showed that the selenium loss in VC-roasted SER meals increased from 7.17 to 19.76% (90-170 °C for 30 min), which was 47.13 to 80.48% of that in DA-roasted SER meals, while no selenium was detected in the SER oils. Compared to DA roasting, VC roasting (90-170 °C for 30 min) reduced lipid oxidation products (LOPs), Maillard reaction products (MRPs), and benzo[a]pyrene contents, and increased carotenoids, unsaturated fatty acid contents, reaching a maximum oil yield of 35.58% at a lower temperature (130 °C for 30 min). Selenium contents exhibited a highly significant negative correlation with MRPs and LOPs (p ≤ 0.005). The VC roasting retarded selenium loss and improved SER oil quality compared to conventional DA roasting.

Evaluation of Thermal Effects on the Bioactivity of Curcumin Microencapsulated with Porous Starch-Based Wall Material Using Spray Drying

Curcumin was microencapsulated by porous starch using a spray dryer with a particle size between 1.5 and 2.0 µm and subjected to water bath (40–100 °C) and oven heating (150–200 °C) in comparison to non-encapsulated samples. The minimum possible encapsulation rate ranged from 26.75 to 52.23%. A reasonable thermal stability was observed after water bath heating with regard to 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH) scavenging activity. On the other hand, the increase in oven heating temperature caused significant alterations compared with the control samples (p < 0.05). The encapsulated particles subjected to oven heating at 170 °C demonstrated serious collapse. The DPPH scavenging activity of non-encapsulated curcumin was significantly reduced (p < 0.05) from 48.94% ± 3.72% (control, 0 °C) to 40.42% ± 2.23% (oven heating, 160 °C); however, remained stable for the encapsulated samples (51.18% ± 4.86%–50.02% ± 1.79%) without significant difference (p < 0.05). The ABTS scavenging activity was promoted as a function of the oven heating temperature. Both DPPH and ABTS free radical scavenging activities remained stable after water bath. Nevertheless, the color of microencapsulated curcumin was better preserved in comparison to the controls.

Seed-Roasting Process Affects Oxidative Stability of Cold-Pressed Oils

The oxidative stability of vegetable oils mainly depends on their fatty acid composition, their degree of unsaturation, and the presence of compounds with antioxidant activity. This paper reports on the effects of the process of roasting oil seeds, prior to pressing them, on the basic characteristics of the oils produced and their oxidative stability. The differential scanning calorimetry (DSC) technique was used to study the process of oxidation of the oil samples in an oxygen-flow cell. Chromatographic analysis revealed that roasting the seeds increased the levels of chlorophyll and β-carotene in all the cold-pressed oils. Similar results were observed for the oil's antioxidant activity, measured by the scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical method. Our results also indicated that roasting seeds prior to pressing them for oil had a positive effect on the oil's stability, as determined by the DSC method. This manifested in both the extension of oxidation induction time and the final oxidation time.

Effect of seed roasting on canolol, tocopherol, and phospholipid contents, Maillard type reactions, and oxidative stability of mustard and rapeseed oils

This work was carried out to study the effect of roasting on different compositional parameters and oil oxidative stability of three Brassica species (Brassica juncea (BJ), B. juncea var. oriental (BJO), and Brassica napus (rapeseed, RS)). After 10 min of roasting at 165 °C, canolol contents of BJ, BJO, and RS oil reached 297.8, 171.6, and 808.5 μg/g, and the phospholipid phosphorus contents reached 453.6, 342.6, and 224.2 μg/g oil, respectively. The BJ and BJO seeds showed more prominent browning reactions than RS, due to the presence of higher amounts of reducing sugars, lysine, arginine and the occurrence of Maillard type browning reactions of phospholipids. The UV-visible spectra, fluorescence, and pyrrole content showed the presence of browning reaction products in the roasted seed oils. Roasting increased the oxidative stability of all varieties. Canolol formation could only partially explain such observations. Other roasting effects such as phospholipid extraction and Maillard type browning reaction products were also responsible for the increased stability.